Fluid pressure reduction device

ABSTRACT

A fluid pressure reduction device comprises a plurality of stacked disks having a perimeter and a hollow center aligned along a longitudinal axis. Each disk has at least one flow path extending between the hollow center and the perimeter, the flow path including an inlet section, an outlet section, and an intermediate section extending between the inlet and outlet sections. Each flow path intermediate section includes a pressure reducing structure and a recovery zone positioned immediately downstream of the pressure reducing structure.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a divisional of prior application Ser. No.09/931,484, filed Aug. 16, 2001 now U.S. Pat. No. 6,701,957.

FIELD OF THE INVENTION

This invention relates to fluid energy dissipation devices and, moreparticularly, to a fluid pressure reduction device with low acousticalconversion efficiency for gas flows and also for devices with cavitationavoidance and hence low noise properties for liquid flows.

BACKGROUND OF THE INVENTION

In the control of fluid in industrial processes, such as oil and gaspipeline systems, power plants, chemical processes, etc., it is oftennecessary to reduce the pressure of a fluid. Adjustable flow restrictiondevices, such as flow control valves and fluid regulators, and otherfixed fluid restriction devices, such as diffusers, silencers, and otherback pressure devices, are utilized for this task. The purpose of thefluid control valve and/or other fluid restricting device in a givenapplication may be to control fluid rate or other process variables, butthe restriction induces a pressure reduction inherently as a by-productof its flow control function.

Pressurized fluids contain stored mechanical potential energy. Reducingthe pressure releases this energy. The energy manifests itself as thekinetic energy of the fluid—both the bulk motion of the fluid and itsrandom turbulent motion. While turbulence is the chaotic motion of afluid, there is momentary structure in this random motion in thatturbulent eddies (or vortices) are formed, but rapidly break down intosmaller eddies which in turn also break down, etc. Eventually viscositydamps out the motion of the smallest eddies and the energy has beentransformed into heat.

Pressure and velocity fluctuations are associated with the turbulentfluid motion that act upon the structural elements of the piping system,causing vibration. Vibration may lead to fatigue failure of pressureretaining components or other types of wear, degradation of performance,or failure of attached instruments. Even when not physically damaging,vibration generates air-borne noise that is annoying to or may damagethe hearing of people.

In industrial applications involving liquids, the chief source of noise,vibration, and damage from the pressure reduction of liquids iscavitation. Cavitation is caused in a flow stream when the fluid passesthrough a zone where the pressure is below its vapor pressure. At thisreduced pressure, vapor bubbles form and subsequently collapse aftertraveling downstream into a zone where pressure exceeds the vaporpressure. The collapsing vapor bubbles may cause noise, vibration, anddamage. Ideally, therefore, a fluid pressure reduction device wouldgradually decrease fluid pressure without dropping below the vaporpressure. In practice, however, such a pressure reduction device isoverly difficult and expensive to produce, and therefore fluid pressurereduction devices are known that use multiple stages of pressurereduction. The final pressure drop in such devices is relatively small,which may produce less bubbles and less cavitation.

Currently there are available fluid control valves containing a valvetrim in the form of stacked disks forming a fluid pressure reductiondevice. The stacked disks define a plurality of fluid flow passagesdesigned to create a pressure reduction in the fluid.

One device using stacked disks has tortuous fluid flow paths formedtherein. In this device, each of the fluid flow passages is designedwith a series of consecutive right angle turns so that the fluid flowchanges directions many times in a tortuous path as the path traversesfrom the inlet to the outlet. In such devices, it is intended for eachright angle turn to produce a discrete pressure drop, so that thetortuous path produces a multi-stage pressure reduction. In reality,however, it has been found that the intermediate right angle turns inthe flow passages do not effectively create a restriction for stagedpressure reduction. In addition, the pressure reduction created by thetortuous path is unpredictable since the pressure reduction effected byeach right angle turn is not known. Furthermore, it has been found thatthe right angle turns may generate pressure and mass flow imbalances andflow inefficiency. The pressure imbalances may lead to the creation oflow pressure areas within the device where the fluid momentarily dropsbelow the vapor pressure and subsequently recovers, thereby creatingcavitation and causing damage. Flow imbalances affect the pressure dropand fluid velocity through the device, wherein a greater mass flowsthrough some passages to result in increased velocity.

In addition, the tortuous path device has passage outlets oriented sothat fluid flow exiting the passages converges. As a result, fluid jetsexiting the adjacent outlets may collide to form a larger jet flowhaving greater stream power, thereby increasing the noise level.

The above recited deficiencies and others in currently available trimdevices significantly reduce the effectiveness of these devices inproviding desired noise attenuation, vibration reduction, and cavitationdamage reduction or elimination. Accordingly, it is desired to eliminatethe above deficiencies as well as to provide other improvements in thetrim devices so as to enable them to provide enhanced noise attenuationcharacteristics.

SUMMARY OF THE INVENTION

In accordance with certain aspects of the present invention, a fluidpressure reduction device is provided comprising a plurality of stackeddisks having a perimeter and a hollow center aligned along alongitudinal axis. Each disk has at least one flow path extendingbetween the hollow center and the perimeter, the flow path including aninlet section, an outlet section, and an intermediate section extendingbetween the inlet and outlet sections. Each flow path intermediatesection includes a pressure reducing structure and a recovery zonepositioned immediately downstream of the pressure reducing structure.

In accordance with additional aspects of the present invention, a fluidpressure reduction device is provided comprising a plurality of stackeddisks having a perimeter and a hollow center aligned along alongitudinal axis. Each disk has at least one flow path extendingbetween the hollow center and the perimeter, the flow path including aninlet section, an outlet section, and an intermediate section extendingbetween the inlet and outlet sections. Each flow path intermediatesection includes a restriction and an associated recovery zonepositioned immediately downstream of the restriction, wherein therestriction directs flow substantially toward a center of the associatedrecovery zone.

In accordance with further aspects of the present invention, a fluidpressure reduction device is provided comprising a plurality of stackeddisks having a periphery and a hollow center aligned along alongitudinal axis. Each disk has at least one flow path extendingbetween the hollow center and the perimeter, the flow path including aninlet section, an outlet section, and an intermediate section extendingbetween the inlet and outlet sections, wherein opposing walls of theflow path intermediate section diverge from one another as the flow pathintermediate section advances from the inlet section to the outletsection.

In accordance with still further aspects of the present invention, afluid pressure reduction device is provided comprising a plurality ofstacked disks having a perimeter and a hollow center aligned along alongitudinal axis. Each disk has first and second flow paths extendingbetween the hollow center and the perimeter, the first flow pathincluding an inlet section, an outlet section, and an intermediatesection extending between the inlet and outlet sections, the second flowpath having an inlet section, an outlet section, and an intermediatesection extending between the inlet and outlet sections. The second flowpath intermediate section and first flow path intermediate section crossat an intersection, and each of the first and second flow pathintermediate sections includes a recovery zone downstream of theintersection.

In accordance with yet additional aspects of the present invention, afluid pressure reduction device is provided comprising a plurality ofstacked disks having a thickness and defining a perimeter and a hollowcenter aligned along a longitudinal axis. Each disk has at least oneflow path extending between the hollow center and the perimeter, theflow path including an inlet section, an outlet section, and anintermediate section extending between the inlet and outlet sections.Each flow path extends across the entire thickness of the disk toprovide a through-cut flow path, each through-cut flow path dividing thedisk into at least first and second blank portions.

In accordance with certain aspects of the present invention, a method ofassembling a fluid pressure reduction device is provided comprisingforming a plurality of disks having at least one flow path extendingbetween a hollow center and a perimeter of the disk, each flow pathincluding an inlet section, an outlet section, and an intermediatesection extending between the inlet and outlet sections, the flow pathdividing the disk into at least first and second blank portions, eachdisk further including a first bridge portion extending between thefirst and second blank portions. The disks are stacked along an axis andsecured together to form a stacked disk assembly. The first bridgeportion of each disk in the stacked disk assembly is then removed.

BRIEF DESCRIPTION OF THE DRAWINGS

The features of this invention which are believed to be novel are setforth with particularity in the appended claims. The invention may bebest understood by reference to the following description taken inconjunction with the accompanying drawings, in which like referencenumerals identify like elements in the several figures and in which:

FIG. 1 is a cross-sectional view illustrating a fluid control valvecontaining a valve trim in the form of stacked disks forming a fluidpressure reduction device in accordance with the teachings of thepresent invention;

FIG. 2 is a plan view of an annular disk which may be used to form eachof the stacked disks in FIG. 1;

FIG. 3 is a plan view of an alternative embodiment annular disk havingrestrictions to create multi-stage pressure reduction;

FIG. 4A is a plan view of yet another alternative embodiment annulardisk for creating multi-stage pressure reduction including a bridge inthe form of an inner ring;

FIG. 4B is a plan view of a disk embodiment similar to FIG. 4A, whereinthe annular disk includes a bridge in the form of an outer ring;

FIG. 4C is a plan view of a disk embodiment similar to FIG. 4A, whereinthe annular disk includes two bridges in the form of inner and outerrings;

FIG. 4D is a plan view of a disk embodiment similar to FIG. 4A, whereinthe annular disk includes a first bridge in the form of an inner ringand a second bridge in the form of a plurality of tabs;

FIG. 5 is perspective view of five disks as in FIG. 4 shown in a stackedassembly;

FIG. 6 is a plan view of an alternative embodiment annular disk whichallows flow to adjacent stacked disks;

FIG. 7 is a perspective view of eight disks as in FIG. 6 shown in astacked assembly;

FIG. 8 is a plan view of an alternative embodiment annular disk havingintersecting flow paths; and

FIG. 9 is a plan view of a still further annular disk embodiment showinga flow path with multiple sub-outlets.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring to FIG. 1, there is illustrated a fluid pressure reductiondevice in accordance with the principles of the present invention in theform of a valve cage 10 having a plurality of stacked disks and mountedwithin a fluid control valve 12. The stacked disks are concentric aboutan axis 29. Fluid control valve 12 includes a valve body 14 having afluid inlet 16, a fluid outlet 18, and a connecting passageway 20through the valve body. While the fluid flow from the inlet 16 to theoutlet 18 is described herein as proceeding from the left to the rightas shown by the arrow in FIG. 1, it will be appreciated that the fluidmay flow in the reverse direction (i.e., from the right to the left)without departing from the teachings of the present invention.

A seat ring 22 is mounted within the valve body passageway 20 andcooperates with a valve operating member 24 to control fluid flow intothe interior and through the exterior of the valve cage 10. The valvecage 10 may be maintained within the valve by conventional mountingmeans such as a cage retainer 26 and mounting bolts 28 engaging thevalve bonnet portion of the valve in a known manner. A series of weldbeads 30 on the outside of the valve cage 10 securely maintains thedisks in an assembled stack. In a constructed preferred embodiment ofthe invention, each individual disk is coated with a nickel plating. Thenickel plated disks are assembled into a stack which is placed in afixture and subjected to a suitable stack loading and temperature tofuse the individual plated disks to each other. In other embodiments,the disks may be brazed or welded together. For large disks, a series ofbolts or other types of mechanical fasteners may be used to securelymaintain the stacked disks assembled.

The valve cage 10 includes a plurality of the stacked disks, each ofwhich is identical to a disk 32 as shown in FIG. 2. The disk 32 includesa hollow center portion 34 and an annular perimeter 36. A plurality offlow paths 38 is formed in the disk 32. Each flow path 38 has an inletsection 40 positioned near the center portion 34, an outlet section 42positioned near the perimeter 36, and an intermediate section 44connecting the inlet section 40 to the outlet section 42. When anidentical disk is stacked on top of the disk 32, and rotatedsufficiently (for example, rotated 60 degrees with respect to the diskshown in FIG. 2), it will be appreciated that the flow paths 46 areentirely contained within each disk 32. In such an embodiment, each flowpath 38 is bounded by an inner wall 46, an outer wall 48, and blankportions of the upper and lower adjacent disks 32.

Each disk 32 has a given thickness “t”, as best shown with reference toFIGS. 1 and 5. In the preferred embodiment, each flow path 38 extendsacross the entire thickness of the disk to provide a through-cut flowpath. The through-cut flow paths may be formed by any one of severalwell-known techniques, including laser cutting. In addition, the flowpaths 38 may be provided in a form other than through-cut passages. Forexample, the flow paths 38 may be formed as grooves or channels in thedisk 32.

Each flow path 38 is shaped to increase the amount of drag exerted onthe fluid. In the embodiment shown in FIG. 2, the intermediate section44 of each flow path 38 is formed in a general spiral shape. The spiralshape maximizes the length of the flow path 38 as it travels from theinlet section 40 to the outlet section 42. The initial width of the flowpath 38 may be selected to ensure that the fluid quickly attaches to theinner and outer walls 46, 48. In the preferred embodiment, the width ofeach flow path 38 may gradually expand to control the velocity of thefluid as the pressure is reduced.

In addition, the flow paths 38 are shaped to reduce noise andcavitation. In this regard, the flow paths 38 avoid closely spaced orconsecutive abrupt changes in direction, defined herein as an includedangle of ninety degrees or less between adjacent flow path portions. Inthe embodiment illustrated in FIG. 2, each flow path 38 is formed in agradual curve without any sharp angles formed between adjacent portionsof the path.

It will be appreciated that, if a reference line 50 were drawn from thedisk axis 29 and a flow path inlet section 40, any portion of the flowpath 38 that extends at an angle to the reference line will increase thelength of the flow path 38 as it travels from the inlet section 40 tothe outlet 42. Any such additional flow path length will increase theamount of drag acting on the fluid, thereby effecting a pressurereduction. When coupled with the absence of closely spaced orconsecutive abrupt direction changes in the flow path 38, the result isgradual reduction in fluid pressure without the creation of adjacentareas of high and low pressures which may cause flow unbalance,reduction in passage efficiency, and areas where low pressure regionsdrop below the liquid vapor pressure, which may lead to flashing andcavitation.

Referring to FIG. 3, an alternative annular disk 60 is shown havingfluid flow paths 62 which produce multi-stage pressure reduction. Eachdisk 60 has a hollow center 64 and a perimeter 66. Each flow path 62extends from an inlet section 68 located near the hollow center 64,through an intermediate section 70, and to an outlet section 72positioned near the perimeter 66. In the embodiment illustrated in FIG.3, the intermediate section 70 of each flow path 62 is formed as aseries of flat leg portions 70 a, 70 b, and 70 c. The leg portions 70a-c are associated with recovery following a pressure reduction stage asthe fluid flows through the flow path 62. Each angle formed betweenadjacent flat leg portions 70 a-c is greater than 90° (i.e., does notform an abrupt direction change as defined herein). The pressurereducing structures, such as restrictions 74, 76, provided in theintermediate section 70 may create discrete pressure drops and mayorient downstream fluid flow. In the illustrated embodiment, therestriction 74 is formed by an inner ridge 78 formed in an inner wall 80of the flow path 62 and an outer ridge 82 projecting from a flow pathouter wall 84. Similarly, the restriction 76 is formed by an inner ridge86 formed in the inner wall 80 and an outer ridge 88 formed in the outerwall 84. It will be appreciated that the restrictions 74, 76 may beformed by a single ridge formed in either the inner or outer walls 80,84, or in any other manner that effects a pressure reduction.

Immediately downstream of each restriction 74, 76 is a recovery zone 90,92, respectively. The recovery zones 90, 92 do not have anyrestrictions, abrupt direction changes, or other pressure reducingstructure therein. As a result, the recovery zones 90, 92 allow thefluid to reattach to the inner and outer walls 80, 84 of the flow path62 so that pressure reducing drag once again acts on the fluid. Therecovery zones 90, 92 also allow for a more predictable pressurereduction through the following restriction so that pressure levels maybe more accurately controlled to avoid dropping below the vapor pressureof the fluid. Still further, any pressure reducing structures locateddownstream of the recovery zone will be more effective since the fluidflow is once again attached to the walls of the flow path 62. As aresult, a true multi-stage fluid pressure reduction device is provided.

The flow path 62 geometry upstream of the restrictions 74, 76 may workin concert with the shape and size of the restrictions 74, 76 to orientthe flow in the recovery zones, thus avoiding larger recirculationzones. As shown in FIG. 3, the outer ridge 82 of restriction 74 islarger than the, inner ridge 78. The offset ridges help direct fluidflow toward the center of the downstream recovery zone 90 to provide amore uniform fluid flow velocity profile and to prevent adjacent areasof high and low fluid pressures and overly large recovery zones. Oneadvantage of a more uniform velocity profile is increased predictabilityfor downstream pressure reduction stages.

The outlet sections 72 are positioned and oriented to minimizeconvergence of fluid exiting from adjacent outlet sections 72. In theembodiment of FIG. 3, the outlet sections are spaced about the peripheryof the disk 60. In addition, adjacent outlet sections are directed awayfrom one another, so that fluid exiting the adjacent flow paths 62diverges.

Referring to FIG. 4A, an annular disk 100 is shown which is quitesimilar to the annular disk 60 of FIG. 3. One of the main differences,however, is in the shape of the intermediate section 70 of each fluidpath 62 a-c. Instead of being flat, as shown in FIG. 3, the leg portions70 a-c of the current embodiment have a gradual curve so that the flowpath 62 a-c more closely resembles a spiral.

The flow paths 62 a-c of the annular disk 100 of FIG. 4A also includerestrictions 74, 76, 77 for producing staged pressure drops. Flow paths62 a and 62 c are shown with restrictions formed by first and secondridges projected from opposite flow path walls, similar to theembodiment of FIG. 3. Flow path 62 b, however, illustrates alternativerestrictions that may be used. Restriction 74 b, for example, is formedby a single ridge projecting from one of the flow path walls.Restriction 76 b is formed by offset ridges 79 a, 79 b projecting fromopposed flow path walls. In addition to being offset, the ridges 79 a,79 b have different profiles. For example, ridge 79 b projects fartherinto the flow path than ridge 79 a. The various restriction embodimentsmay be used to obtain the desired flow characteristics such as pressuredrop and fluid flow orientation.

The disk 100 of FIG. 4A also includes a bridge, such as inner ring 102formed at the hollow center of the disk 100, for facilitatingmanufacture and assembly of multiple disks to form the trim cage.Without the inner ring 102, each disk would be formed of separate,spiral-shaped blank pieces 104 which would be difficult to transport andassemble. With the inner ring 102, the blank pieces 104 are held inposition while the disks are stacked and secured together with relativeease. The hollow center of the trim cage is then enlarged to its finaldiameter by removing the inner ring 102 to establish fluid communicationbetween the hollow center and the inlet sections 68. Instead of theinner ring 102, each disk may have an outer ring 105 (FIG. 4B) thatprovides the same benefits as the inner ring. The outer ring 105 is thenremoved once the disks are assembled. Furthermore, the disks may beprovided with both inner and outer rings 102, 105, as illustrated inFIG. 4C, to further stabilize the disks during assembly of the trimcage. Still further, the bridge may be provided in the form of one ormore tabs 106 (FIG. 4D) extending between adjacent blank pieces 104. Thetabs 105 are removed after the disks are assembled. In any of theforegoing embodiments, the bridge may be removed by any known means,such as by honing, grinding, or machining.

The above-noted bridge is not necessary for alternative flow pathconstructions, such as grooves or channels, where individual blankpieces are not created. In such alternatives, the flow paths 38 may beformed during casting or formation of the disk, etched into the surfaceof the disk, or in any other suitable manner.

FIG. 5 provides a perspective view of a plurality of stacked annulardisks 100. From FIG. 5, it will be appreciated that adjacent annulardisks 100 may be rotated with respect to each other to create the flowpaths 62. In the illustrated embodiment, the inner rings 102 of thestacked disks 100 have not yet been removed to expose the inlet sections68 of each flow path 62.

Referring to FIG. 6, an alternative embodiment annular disk 110 is shownin which each fluid flow path 62 traverses more than 1 disk. In theillustrated embodiment, the intermediate section 70 includes an upstreamportion 112 having an exit end 114 and a downstream portion 116 havingan entrance end 118. As shown in FIG. 7, multiple identical disks 110may be formed and stacked so that the exit end 114 of the upstreamportion 112 formed in a first disk 110 registers with the entrance end118 of the downstream portion 116 formed in a second disk 110. As aresult, fluid will flow from the hollow center through the upstreamportion 112 of the first disk to the exit end 114. The fluid will thentransfer via the overlapped exit and entrance ends 114, 118 to thedownstream portion 116 of a second disk.

The transition between the first and second disks creates a pressurereducing structure in the form of two consecutive 90° direction changes.To minimize the deleterious effects of the closely spaced abruptdirection changes, each downstream flow path portion 116 includes arecovery zone 120 immediately downstream of the entrance end 118. Therecovery zones 120 allow the turbulence in the fluid to dissipate andpromote reattachment of the fluid to the flow path walls. As a result,even through a series (i.e., a pair) of consecutive abrupt directionchanges may be provided, the pressure drop created thereby is morepredictable and the gradual effect of drag is enhanced. In analternative, the exit and entrance ends 114, 118 may be shaped to effecta smooth transition from one disk to the next, thereby avoiding thecreation of consecutive abrupt direction changes.

FIG. 8 shows another disk embodiment having intersecting fluid flowpaths so that the collision of fluid in the paths reduces fluidpressure. The disk 130 includes three inlet sections 132 formed at thehollow center 134 of the disk. Each inlet section 132 may be a commoninlet section for two associated flow paths. For example, common inletsection 132 feeds fluid to flow paths 136, 138. Each flow path 136, 138has a generally spiral shape from the inlet section 132 to an outletsection 140. Each inlet section 132 is preferably radially aligned witha center point of the hollow center 134, so that each flow path 136, 138receives approximately one half of the fluid entering the associatedinlet section 132. Because of the abrupt direction change between theinlet section 132 and the flow paths 136, 138, recovery zones 142, 144are provided in each flow path 136, 138 immediately downstream of theinlet section 132.

Each flow path 136, 138 includes pressure reducing structure in the formof flow path intersections. As each flow path 136, 138 extends toward aperimeter 146 of the disk 130, it intersects with other flow paths. Forexample, flow path 138 intersects with a flow path 148 at intersection150. Flow path 138 further crosses a flow path 152 at intersection 154.Finally, flow path 138 intersects flow path 136 at intersection 156.Each flow path is provided with sufficient recovery zones downstream ofeach intersection. For example, flow path 138 is formed with a recoveryzone 158 between intersections 150 and 154. In addition, recovery zone160 is provided between intersections 154 and 156.

In operation, it will be appreciated that the fluid passing through theflow paths will collide at the intersections. The fluid collisionsdissipate energy in the fluid and reduce fluid pressure. As a result,the fluid's own motion is used enhance energy dissipation and effect apressure reduction.

The flow paths may be co-planar so that each intersection creates anabrupt change in direction of the fluid flow. At intersection 150, forexample, fluid traveling through flow path 138 may reach theintersection 150 and deflect into the downstream portion of fluid path148, as suggested by arrow 162. Likewise, fluid in the upstream portionof flow path 148 may reach the intersection 150 and deflect into adownstream portion of the flow path 138, as suggested by arrow 164.Fluid flowing through these paths, therefore, may experience an abruptchange in direction. While normally the abrupt change in direction mayresult in undesirable flow characteristics, the recovery zones provideddownstream of each intersection, such as recovery zone 158, minimize thedetrimental effects of such abrupt direction changes and allow thepressure drop associated therewith to be more predictable. As a result,the desired total pressure drop through the disk 130 may be morereliably calculated and designed.

Alternatively, the flow paths may be offset prior to each intersectionto reduce or eliminate abrupt direction changes in the fluid flow whilestill creating additional losses through the action of a fluid shearlayer between the two streams. As shown in FIG. 8, flow path 136 mayintersect with flow path 166 at intersection 168. Upstream of theintersection 168, flow path 136 may include a ramp 170 which directsfluid flow toward an upper portion of the intersection 168, while flowpath 166 may include a ramp 172 which directs fluid flow toward a lowerportion of the intersection 168. As a result, fluid flowing from paths136, 166 into intersection 168 will continue along their respectivepaths, without abruptly changing direction. While the pressure drop atthe intersection 168 is not as great as that associated with planarintersection 150, energy in the fluid is dissipated due to shear forcescreated by the adjacent fluid flow streams.

Referring now to FIG. 9, an annular disk 190 is shown having multiplesub-outlets 192. A flow path 62 is formed in the disk 190 having aninlet section 68, an intermediate section 70, and an outlet section 72.The inlet section 68 and intermediate section 70 may be formed in any ofthe manners described above with reference to the various embodiments.The outlet section 72, however, includes a splitting sub-flow section192 that forms first and second sub-flow outlets 194. The multiplesub-flow outlets 194 increase the amount of contact between the fluidand the path walls, thereby increasing viscous drag.

While the present description is directed to including the fluidpressure reducing device of this invention in a throttling fluid controlvalve, it is understood that the invention is not so limited. The devicemay be implemented as a fixed restriction in a pipeline either upstreamor downstream of a control valve, or entirely independent of thelocation of a control valve.

The foregoing detailed description has been given for clearness ofunderstanding only, and no unnecessary limitations should be understoodtherefrom, as modifications will be obvious to those skilled in the art.

1. A fluid pressure reduction device comprising: a plurality of stackeddisks having a perimeter and a hollow center aligned along alongitudinal axis; and each disk having at least a first and a secondflow path, each flow path having a generally spiral shape andcontinuously extending between the hollow center and the perimeterwherein at least the first and second flow paths spiral in generallyopposite directions and the opposing walls of each flow path graduallydiverge, each flow path being further comprised of an inlet section, anoutlet section, and an intermediate section extending between the inletand outlet sections; wherein each flow path crosses at least one otherflow path at at least one intersection; and wherein each of the flowpath intermediate sections includes a recovery zone downstream of theintersection.
 2. The fluid pressure reduction device of claim 1, inwhich the flow paths are directed toward the intersection atsubstantially the same plane, so that fluid flowing through each flowpath undergoes an abrupt direction change at the intersection.
 3. Thefluid pressure reduction device of claim 1, in which at least the firstflow path includes a first ramp upstream of the intersection directed toa first plane and the second flow path includes a second ramp upstreamof the intersection directed to a second plane, so that fluid flowingthrough at least the first and second flow paths creates shear forces atthe intersection.
 4. The fluid pressure reduction device of claim 1, inwhich a common inlet section provides fluid entry for at least the firstflow path and second flow path.
 5. The fluid pressure reduction deviceof claim 4, in which the common inlet section is aligned along a radialdisk reference line extending from the axis to the common inlet sectionso that substantially equal volumes of fluid enter the first and secondflow paths.
 6. A fluid pressure reduction device comprising: a pluralityof stacked disks having a perimeter and a hollow center aligned along alongitudinal axis; and the plurality of stacked disks defining at leastone flow path extending between the hollow center and the perimeter, theflow path including an inlet section, an outlet section, and anintermediate section having a generally spiral shape and extendingbetween the inlet and outlet sections, the flow path including apressure reducing structure and a recovery zone positioned immediatelydownstream of the pressure reducing structure; wherein a first disk ofthe plurality of stacked disks includes the inlet section and anupstream portion of the intermediate section, and a second disk of theplurality of stacked disks located adjacent the first disk includes theoutlet section and a downstream portion of the intermediate section, theintermediate section upstream portion fluidly communicating with theintermediate section downstream portion.